Southern — 3Ionograph of the British and Irish Oligochceta. 121 



are — Chcetogaster crystallinus, C. diastrophus, Nais ohtusa, and JEolosoma Hem- 

 prichi. No distinction can be drawn between the OligochEete fauna of the 

 slow lowland streams, and that inhabiting ponds and lakes. Tubifex rivulo- 

 runi, however, is almost confined to ponds and lakes, and is seldom found in 

 rivers. The most characteristic species found in these lakes and streams are— 



Stylaria lactistris. Tubifex rivuloriun. 



Chcetogaster crystallinus. T. ferox. 



C. diastrophus. Zimnodrilus parvus. 



Nais elinguis. L. udekemianus. 



iV. ohtusa. Lumbriculus variegatus. 



JEolosoma variegatum. Stylodrilus Hallissyi. 



2. Geographical. 



The only species of Lumbricidte peculiar to the British Isles are Eiseniella 

 macrura (Friend) and Helodrilus relictus n, sp. Both these species have 

 been described from single specimens. The former was described by Friend 

 in 1893, from a specimen found in Dublin; and it has not since been observed. 

 The var. tetragonura of Eiseniella tetraedra was described by Friend, from 

 Bangor, North Wales ; and it has not been found elsewhere. The validity of 

 these three forms is not yet satisfactorily established. 



I have examined the distribution of our endemic earthworms in order to 

 find out whether they fall into the usual geographical groups which are 

 believed to constitute our native fauna. These are four in number : 

 (1) North American, (2) Northern and Alpine, (3) Lusitanian, (4) Germanic. 

 The area where endemic species of Lumbricidse are found embraces Europe, 

 Asia (except the south-east), and the eastern portion of Canada and the United 

 States. The greater number of species is found in the districts to the north 

 and north-east of the Mediterranean ; and the centre of radiation for the 

 family was probably in this region. 



Many of our species are found widely spread over the whole of this 

 region, and consequently their place of origin cannot be determined. Of the 

 29 species and sub-species of earthworms found in the British Isles, 11 fall 

 into this class. These are — 



Eiseniella tetraedra. Helodrilus ruhidus typ. 

 Eiseniafodida. var. suhruhicunda. 



E. rosea. H. octaedrus. 



Helodrilus caliginosus typ. Lumhincus ruhellus. 



var. trapezoides. L. castaneus. 



L. terrestris. 



[U-] 



